Fixing device and image forming apparatus

Abstract

A fixing device including: a heated fixing member to fix a toner image on a recording medium; a pressing member to form a nip portion between the pressing member and the fixing member; a first blowing unit that blows air to a position close to a leading edge of the recording medium; and a second blowing unit that blows air to the recording medium, wherein a discharge pressure of the air discharged by the first blowing unit is larger than that of the air ejected by the second blowing unit; a discharged air volume discharged by the first blowing unit is less than that discharged by the second blowing unit; and a first discharge port from which air is blown by the first blowing unit is arranged upstream of a second discharge port from which air is blown by the second blowing unit.

1. A fixing device comprising:
 a heated fixing member; 
 a pressing member to form a nip portion between the pressing member and the fixing member, wherein the fixing member and the pressing member fix a toner image on a recording medium; 
 a first blowing unit that separates the recording medium from the fixing member by blowing air to a position close to a leading edge of the recording medium having passed the nip portion; and 
 a second blowing unit that separates the recording medium by blowing air to the recording medium whose leading edge has passed through the nip portion, 
 wherein a discharge pressure of the air discharged by the first blowing unit is larger than a discharge pressure of the air discharged by the second blowing unit; 
 a discharged air volume discharged by the first blowing unit is less than a discharge air volume discharged by the second blowing unit; and 
 a first discharge port from which air is blown by the first blowing unit is arranged upstream of a second discharge port from which air is blown by the second blowing unit in a direction of conveyance of the recording medium; 
 wherein the first blowing unit discharges air compressed by an air compressor and the second blowing unit discharges air ventilated by a fan. 
 
     
     
       2. The fixing device of  claim 1 , wherein a blowing position of the fixing member, to which the air from the first blowing unit is blown to, is a position to which the leading edge of the recording medium reaches along an outer surface of the fixing member within 20 msec from an exit of the nip portion. 
     
     
       3. The fixing device of  claim 2 , wherein the first blowing unit is adapted to blow air from the first blowing unit to the blowing position within an area of an angle made by a tangent to the fixing member at the blowing position and an extension line from the nip portion. 
     
     
       4. The fixing device of  claim 1 , wherein a plurality of the first discharge ports and a plurality of the second discharge ports are arranged in the across the width direction of the recording medium to be fixed; and the fixing device is provided with a control unit wherein, when fixing the recording medium narrower than the widest recording medium that can be fixed, control is provided in such a way as to suspend a blowing of air from the first and second discharge ports which are located at an end in the across width direction of the recording medium and which do not contribute to separation of the recording medium. 
     
     
       5. The fixing device of  claim 4 , further comprising a plurality of electromagnetic valves communicating with the first discharge ports respectively, and a plurality of fan switches communicating with the second discharge ports, wherein the control unit controls on-off operations of the electromagnetic valves and fan switches. 
     
     
       6. An image forming apparatus comprising:
 an image forming section for forming a toner image; 
 a transfer section for transferring the toner image onto a recording medium; and 
 a fixing device for fixing the toner image on the recording medium, 
 
       wherein the fixing device includes:
 a heated fixing member; 
 a pressing member to form a nip portion between the pressing member and the fixing member, wherein the fixing member and the pressing member fix a toner image on a recording medium; 
 a first blowing unit that separates the recording medium from the fixing member by blowing air to a position close to a leading edge of the recording medium having passed the nip portion; and 
 a second blowing unit that separates the recording medium by blowing air to the recording medium whose leading edge has passed through the nip portion, 
 wherein a discharge pressure of the air discharged by the first blowing unit is larger than a discharge pressure of the air discharged by the second blowing unit; 
 a discharged air volume discharged by the first blowing unit is less than a discharge air volume discharged by the second blowing unit; and 
 a first discharge port from which air is blown by the first blowing unit is arranged upstream of a second discharge port from which air is blown by the second blowing unit in a direction of conveyance of the recording medium; 
 wherein the first blowing unit discharges air compressed by an air compressor and the second blowing unit discharges air ventilated by a fan. 
 
     
     
       7. The image forming apparatus of  claim 6 , wherein a blowing position of the fixing member, to which the air from the first blowing unit is blown to, is a position to which the leading edge of the recording medium reaches along an outer surface of the fixing member within 20 msec from an exit of the nip portion. 
     
     
       8. The image forming apparatus of  claim 7 , wherein the first blowing unit is adapted to blow air from the first blowing unit to the blowing position within an area of an angle made by a tangent to the fixing member at the blowing position and an extension line from the nip portion. 
     
     
       9. The image forming apparatus of  claim 6 , wherein a plurality of the first discharge ports and a plurality of the second discharge ports are arranged in the across the width direction of the recording medium to be fixed; and the fixing device is provided with a control unit wherein, when fixing the recording medium narrower than the widest recording medium that can be fixed, control is provided in such a way as to suspend a blowing of air from the first and second discharge ports which are located at an end in the across width direction of the recording medium and which do not contribute to separation of the recording medium. 
     
     
       10. The image forming apparatus of  claim 9 , wherein the fixing device further comprising a plurality of electromagnetic valves communicating with the first discharge ports respectively, and a plurality of fan switches communicating with the second discharge ports, wherein the control unit controls on-off operations of the electromagnetic valves and fan switches.